The invention relates generally to a fuel container of plastic material and more particularly a fuel container in the form of a fuel tank of plastic material, for example for a motor vehicle.
A typical form of a fuel container of plastic material comprises one or more welded seams acting as seam locations for affording structural integrity of the container body and/or in the form of connecting or sealing seams between a wall portion of the container body in the region of openings therethrough and closure elements or covers which are thereby secured to the container body. There is a wide range of different design configurations of fuel containers of that kind, for example as motor vehicle fuel tanks, which substantially comprise polyethylene. Such fuel containers of plastic material are to a greater or lesser degree permeable in relation to hydrocarbons, and, in the case of containers consisting of a single layer of polyethylene, hydrocarbons can fairly readily diffuse through the wall of the container.
A level of permeability which is markedly reduced in comparison with single-layer fuel containers or tanks of polyethylene is achieved in the case of fuel containers which are of a multi-layer wall structure, with diffusion-type barrier layers incorporated therein. Such containers are predominantly produced by an extrusion blow molding procedure. However even such containers may not be completely gas-tight. Problems arise in connection with such containers in relation to connecting elements such as valves and nipples which may necessarily be provided on the container, as well as the welded seams, through which hydrocarbons can still diffuse, as in the region of the welded seams the barrier layers are not directly welded to each other but in very thin residual layers are separated by material which has little barrier effect.
This problem is already addressed in WO 00/48859. To resolve that problem, it is proposed therein that a fuel tank is provided with a cover of a hood-like configuration, which forms, between itself and the outer wall surface of the tank, a cavity which is in the form of a fuel vapor collecting chamber and which encloses the seams of the tank as well as various connecting openings and cover members thereon. That hood-like cover is connected by welding to the outside wall surface of the tank. Such a structure is extremely complicated and expensive and in addition such a design configuration still allows hydrocarbons to be discharged to the ambient atmosphere through the welded seams of the hood-like cover.
Consideration may also be given to DE 198 53 097 A1 disclosing for example a fuel container or tank which is composed of two halves and which has a wall produced from plastic material by an injection molding procedure. Each half of the tank in turn comprises shell portions which are arranged in mutually superposed relationship and between which a slit or gap is left free. Fuel vapors which have passed into that gap are removed therefrom and filtered. Such a design configuration still involves the problem that the welded seams of the tank represent potential weak points.
An object of the present invention is to improve a fuel container of plastic material, such that it discharges as little fuel vapor to the ambient atmosphere as possible.
Another object of the present invention is to provide a fuel container of plastic material which, while affording appropriate structural integrity, can satisfy demands made thereon in terms of emission of fuel vapors to the atmosphere, without entailing a complex design configuration.
Still another object of the invention is to provide a fuel container of plastic material, so designed as to avoid serious fuel vapor emissions to the ambient atmosphere without involving major structural steps for completely sealing off welded seams of the fuel container.
In accordance with the principles of the present invention the foregoing and other objects are attained by a fuel container of plastic material, for example a motor vehicle tank, comprising one or more welded seams as seam locations of the container body and/or as connecting or welding seams between a wall of the container body in the region of at least one opening and a closure element or cover welded thereto. At least one of the welded seams is at least partially penetrated by a duct which extends in the longitudinal direction thereof. The duct can be filled with air and vented of air for ventilation purposes.
As will be seen in greater detail from preferred embodiments of the invention as described hereinafter instead of requiring total and complete sealing of the welded seams of the container, which can be achieved only at the cost of extremely high structural complication and expenditure, in general terms, the invention aims to provide for ventilation of the welded seams by means of the duct passing therethrough, which can be implemented using simple means.
In a preferred feature of the invention the duct can have connections for filling and venting, at each end.
In a further preferred feature the connections can be provided with valves, for example for air-filling or venting purposes.
In the case of a fuel container which was produced by extrusion blow molding from a multi-layer preform, a preferred feature can provide that the duct was produced by recesses or openings in the edges of the blow molding mold.
When the fuel container is made from two half-shell portions which are welded together, with the half-shell portions being respectively welded together at connecting flanges thereon, the connecting flanges can each have groove-shaped openings forming at least one duct.
As an alternative thereto the fuel container can be formed from two half-shell portions which are welded together at their ends, with at least one duct being kept free between two peripherally extending steps or shoulders of the half-shell portions.
In a further preferred feature of the invention the seam location of the container body, which includes a respective duct, can be penetrated in a portion-wise manner by the duct, wherein a plurality of duct portions can communicate with a common venting conduit. Venting of at least one duct can be effected by way of a filter element, preferably by way of an activated carbon filter which is in any case associated with the fuel container.
Finally, means can be provided for pressure filling at least one duct with air. The flushing air which is introduced into the duct in that way can be passed to the internal combustion engine which is fed with fuel from the fuel container, or to an activated carbon filter which is in any case present in a motor vehicle. Ventilation of the passages can be effected both by means of a reduced pressure and also by means of an increased pressure.
It will be assumed however that the introduction of air will automatically occur by virtue of the drop in concentration of the hydrocarbon vapors, in a duct according to the invention, when that duct for example is connected to a filter element.
Further objects, features and advantages of the invention will be apparent from the description hereinafter of preferred embodiments thereof.